Fe-catecholate and Fe-oxalate vibrations and isotopic substitution shifts from DFT quantum chemistry
Artikel i vetenskaplig tidskrift, 1999

Quantum chemical model calculations using density functional theory (DFT) were used to assign iron-catecholate and iron-oxalate vibrations and to get quantitative predictions of the isotopic shifts. Full geometry optimizations and vibrational analyses were performed for catechol, Fe(catecholate)(2-), Fe(4-methylcatecholate)(2-), [Fe(oxalate)(3)](3-), and Fe(oxalate)(2-). The advantages of Fe(0) versus Fe(III) models rue discussed. For selected systems O-16/18, Fe-54/57, and H-1/2 isotopic substitution shifts are reported. They were successfully matched to experimental patterns from recent resonance Raman studies of tyrosine hydroxylase and allowed more precise assignments of the observed bands. The nature of the catecholate C=O and Fe-O vibrations were clarified, and the existence of a chelate vibration mode was confirmed. A band predicted at similar to 320 cm(-1) was assigned to a new vFe-O vibration with a large Fe-54/57 isotope effect, and no significant Fe-54/57 shifts were observed for the other Fe-O vibrations. We note that with the commonly used diatomic harmonic oscillator model one can only make a rough estimation of these shifts. DFT model calculations are suggested as a more precise tool when interpreting isotopic substitution shifts in vibrational spectra.

ferric soybean lipoxygenase-1

normal-coordinate

4-dioxygenase

iron

density-functional theory

tyrosine-hydroxylase

raman-spectroscopy

protocatechuate 3

crystal-structure

spin-densities

complexes

resonance

Författare

Lars Öhrström

Institutionen för oorganisk kemi

I. Michaud-Soret

Journal of Physical Chemistry A

Vol. 103 256-264

Ämneskategorier

Kemi